Process for producing delta7-3-hydroxy steroids



United States Patent PROCESS FOR PRODUCING A"-3-HYDROXY STEROIDS John M.. Chemerda and William V. Ruyle, Metuchen, N. J., assignors to Merck & (10., Inc., Rahway; N. 1., a corporation of New Jersey 7 No Drawing. Application March 3, 1951 Serial No. 213,807

4 Claims. (Cl. 260397.2)

This invention relates to compounds of the cyclopentanopolyhydrophenanthrene series, and more particularly to a process for the preparation of cyclopentano polyhydrophenanthrene compounds having a double bond in the 7:8 position from the corresponding compounds having conjugated double bonds in the 5:6 and 7:8 positions. Cyclopentanopolyhydrophenanthrene compounds unsaturated in the 7 :8 position are useful as intermediates in the preparation of other steroid compounds. For example, they :are useful as starting materials for preparing steroid compounds having a functional group in ring C at the 11 position as described in copending application 7 Serial No. 215,026, filed March 10, 1951.

It is an object of our present invention to provide a process for preparing cyclopentanopolyhydrophenanthrene compounds having a double bond in the 7:8 position. It is :a further object to provide a practical process for selectively hydrogenating a double bond in the 5:6 position in a steroidal compound having conjugated bonds in the 5:6 and 7:8 positions to obtain the corresponding steroid having a double bond in position 7:8. Other objects will be apparent from the detailed description hereinafter provided.

In accordance with our invention, this desideratum is achieved by reacting a cyclopentanopolyhydrophenanthrene compound having conjugated double bonds in the 5:6 and 7:8 positions with hydrogen at superatmospheric pressure in the presence of Raney nickel catalyst. Under these reaction conditions, we have found that the 5:6 double bond is saturated without affecting the unsaturated bond in the 7:8 position. v

In carrying out our invention we have obtained excellent yields of the desired product by effecting the reduction in an inert solvent medium. Suitable solvent inediums suitable for'use in ourprocess are benzene, toluene, 'xylene, petroleum hydrocarbons, lower aliphatic alcohols, dioxane, and the like. It is necessary to avoidusing acidic or halogenated solvents as reaction'mediums since such solvents react with Raney nickel catalyst and result in inactivating the catalyst. Generally, we find that optimum yields of the desired product are obtained by effooting the reduction at about room temperature and under a hydrogen pressure of 1 to 3atmospheres, although higher temperatures and pressures mayalso be utilized. 7

After the hydrogenation is completed, the desired cyclopentanopolyhydrophenanthrene" compound having an' unsaturated bond in the 7 :8 position isreadily re- 2,840,574 Patented June 24, 1958 covered from the reaction product by removing the suspended catalyst, and concentrating the resulting solution. The residue so obtained may be purified by recrystallization from appropriate solvents in accordance with conventional chemical practice. H

The process of our invention can be utilized to selectively hydrogenate various cyclopentanopolyhydrophenanthrene compounds having conjugated double bonds in the 5 :6 and 7:8 positions to saturate the 5 :6 double bond. Suitable starting materials for the process of our invention that might be mentioned include (1) Naturally occurring sterols, having a conjugated double bond system in the 5:6 and 7:8 positions, such as ergosterol and its stereoisomers, lumisterol and pyr'ocalciferol.

(2) 7-dehydro sterols, such as 7-dehydrocholesterol and 7-dehydrostigmasterol which are readily prepared from cholesterol and stigmasterol in accordance with processes described in the literature. V

(3) 7-dehydroderivatives of sapogenins such as 7-dehydrodiosgenin, 7-dehydrobotogenin, and 7-dehydroyuccagenin.

(4) Steroid compounds having the conjugated double bonds in the 5 :6 and 7:8 positions such as 3-hydroXy-A bisnorcholadienic acid and 3 hydroxy A pregnadienone-20.

Generally, when the starting'compound contains a hydroxy substituent, we find it desirable to convert this substituent to an acyloxy group since the acyl derivatives are more readily soluble in organic solvents. Acyloxy derivatives such as those of the lower aliphatic acids, for example acetoxy, propionoxy, and the like are particularly; satisfactory in our process, although other acyloxy derivatives may also be utilized. Similarly, we prefer to use an ester of a steroid acid since these products are more soluble in organic solvents. Since the lower alkyl esters such as methyl or'ethyl are readily and conveniently prepared, we ordinarily preferto use such esters, although any ester can be used. his indeed surprising to find that it is possible to selectively hydrogenate the unsaturated bond in the 5:6 position Without affecting the double bond in the 7:8 position, or causing the double bonds to shift or migrate to other positions. Previously, other investigators had found that hydrogenation of compounds containing conjugated double bonds in the 5 :6 and 7:8 positions caused the double bond in the 7 :8 position to shift to the 8:14 position. On the contrary in our improved process the desired products having a double bond in the 7:8 position are obtained in excellent yields and in substantially pure form indicating that essentially no migration or shifting of the double bonds occurs. Further, it was also unexpected to find that the'do'u'ble bonds in the side chains of compounds such as ergosterol or 7-dehydrostigmasterol are not simultaneously hydrogenated in our process, but remain unsaturated thereby providing a means of readily degrading the side chain of such compounds.

Thus, we have prepared 7-dehydrotigogenin and 3-.

i 3 The product, 7-dehydrotigogenin, is conveniently prepared by selectively hydrogenating 3-acyloxy-7-dehydrodiosgenin in the presence of Raney nickel to obtain the corresponding 3-acyloxy-7-dehydrotigogenin compound which is readily hydrolyzed with alkali to the 3-hydroxy compound. Similarly, 3-hydroxy-A"-allopregnenone-ZO is prepared by selectively hydrogenating 3-acyloxy-A -pregnadienone-ZO, and subjecting the resulting 3-acyloxy-A"- a1lopregnenone-20 to hydrolysis. Although various acyl derivatives of these compounds can be used in this selective hydrogenatiomwe usually prefer to use a lower aliphatic acid ester such as. the 3-acetoxy, 3-propionoxy, and the like for this purpose.

The following examples are presentedto illustrate specific embodiments of our invention.

EXAMPLE 1 Preparation of A' -3-acetoxyergostadierte With the aid of about 4.5 g. of Raney nickel suspension in alcohol, 17.5 g. of ergosteryl acetate in 550 ml. of dioxanewas hydrogenated at an initial pressure of 34 atmospheres at ordinary temperature (2040 C.). After two hours, the rate of hydrogenation was extremely slow and themixture was filtered free of catalyst. After removal of dioxane under reduced pressure, the residue was triturated with hot methanol and 15.0 g. of A -3- acetoxyergostadiene was isolated by filtration of the cooled mixture; M. P. ISO-183 C., a -24 (2.16% CHCI EXAMPLE 2 Preparation of A -3-acetaxyergostadiene The hydrogenation shown in Example 1 was also carried outin a benzene medium as follows:

The ordinary Raney nickel suspension was decanted free of alcohol and the residue washed several times with benzene to remove alcohol. With the aid of about 7 g. of this benzene-washed Raney nickel preparation, 61 g. of ergosterol acetatein 500 cc. of benzene was hydrogenated at an initial pressure of 3-4 atmospheres until 1.2-1.50molar proportions of hydrogen had been absorbed. Thereupon the catalyst was removed by filtration, the filtrate concentrated in vacuo, the residue digested with 200 cc. of boiling acetone and after one crystal- .lization of the product, pure A -3-aeetoxy-ergostadiene was obtained in 66% yield; M. P. 182-184.5 C., a .-19i1 (2% CHClg). A phase solubility determination indicated that the material was 99:1% pure.

12.75 g; 'of methyl 3-acetoxy-A -bisnorcholenate was dissolved in 300 cc. of a purified low-boiling petroleum fraction (Skellysolve B), and the resulting solution was distilled until 50 cc. of solvent had been removed. 6.2 g. of N-bromosuccinimide was added to the resulting solution, and the mixture was illuminated for a 15 minute period with a photo-flood lamp (No. 4A), at the end of which time all of the N-bromosuccinimide had reacted. The reaction mixture was cooled and filtered, and the resulting solution was evaporated to small volume and cooled in a Dry Ice-acetone bath. The product which crystallized was filtered and dried to give 8.97 g. of crude methyl 3-acetoxy-7-bromo-A -bisnorcholenate; M. P. 114- C. This product was purified by recrystallization from petroleum ether (Skellysolve B) to give substantially pure methyl 3-acetoxy-7-brorno-M-bisnorcholepate; M. P. 1l9120 C.

Crude methyl 3-acetoxy-7-bromo-A -bisnorcholenate was heated under reflux with approximately an equal weight of gamma-collidine in approximately 5 volumes of xylene for a period of approximately 20 minutes. The reaction mixture, containing suspended collidine hydro bromide, was cooled to 0 C. and washed successively with ice water, with ice cold 1 N aqueous hydrochloric acid, with cold saturated sodium bicarbonate solution, and finally with ice water. The xylene layer was then dried and evaporated to small volume under reduced pressure. The resulting solution was digested with acetone, and the crystalline material which separated was recovered by filtration. It was found to be a mixture of methyl 3- acetoxy-A -bisnorcholadienate and methyl S-acetoxy- M -bisnorcholadienate, as indicated by the absorption spectrum. Attempts to separate the components of the mixture by recrystallization were not satisfactory. The mixture was therefore subjected to chromatography, utilizing activated alumina, whereby pure methyl 3-acetoxy- A -bisnorch0ladienate was obtained; M. P. 150 C.

EXAMPLE 4 Preparation of methyl 3-acetoxy-A' -bisnorallocholenate A solution of'5 g. of methyl 3-acetoxy-A -bisnorcholadienate (prepared as described in Example 3) in 100 ml.

AeO

of benzene was shaken with 1.5 g. of Raney nickel (specially prepared free of ethanol) under hydrogen at 3 atmospheres pressure. After slightly more than the theoretical amount of hydrogen had been absorbed, the catalyst was removed by filtration, and the filtrate was concentrated to dryness. The residue was washed with 25 ml. of methanol, and dried. Yield 4.35 g., M. P. ISO- C. After two recrystallizations from methanol the product, obtained as large plates, melted at 156- 157 C., [c.1 5.5 (C.=0.910 in CHCl The acetate was saponified by refluxing with 1 N methanolic potassium hydroxide to give methyl 3-hydroxy-A' -bisnorcholenate, M. P. 179-181 C., [a] =6.5 (C.=1.00 in CHCl The benzoate, prepared with benzoyl chloride and pyridine in the usual way, and recrystallized from acetone in leaflets, melted at 169- 170' C.

CH GE CHI N-bromosucclnimlde Diosgenln 3-acetate 7-bromo dlosgenln-a-acetate -gl g m 7-dehydrodiosgenln-S-acetate A solution containing 4.57 g. (0.01 mol) of diosgeninfrom acetone to give 0.83 g. of crude 7-dehydrodiosgenin- 3-acetate dissolved in 100 ml. of carbon tetrachloride was 3-acetate which was obtained in the form of needles; distilled until 20 cc. of the distillate had been collected. M. P. 175-l88 C. The absorptionspectrum of this ma- The solution was allowed to cool slightly, and 1.96 g. terial indicated that it was a mixture of A and A- (0.011 mol) of N-bromosuccinimide was added to the diene isomers.

solution. The resulting mixture was illuminated with a Max photofiood lamp (No. RFL-2) for a period of 6 minutes, (2 A 7 E1 during which time the reaction mixtureboiled vigorously, 2390 4 the volatile components being returned to the reac- 2480 tion mixture as reflux. The reaction mixture was then 16 h m '7 cooled, and the insoluble material was removed there- 40 2710 on 167 from by filtration. The filtered solution was evaporated 2820 '5' u 176 in vacuo until a greenish, viscous oil remained. Upon 2930 the addition of petroleum ether (B. P. 30-60 C.) crystallization of the oiloccurred. The crystalline material This mixture was recrystallized twice from methanol was slurried with petroleum ether, fitered, and washed 4 to give elongated flat plates of the A -diene isomer in with petroleum ether to give 3.25 g. of 7-bromo-diosgeninsubstantially pure form; M. P. 195-203 C.

EXAMPLE 6 7 Preparation of 3-acetoxy-7-dehydrotigogenin I Q Hal om 5.0170011.

Raney N1 Hi ACO r'r 7-dehydrodlosgenlu acetate I a-acetoxy-7-dehydrotlgozentn 3-acetate; M. P. 143-145 C., dec. This material was A solution of 2.87 g. of 7-dehydrodiosgenin acetate further purified by recrystallization from acetone to. give (prepared as described in Example 5 by reacting diosgenin small needles; M. P. 151-154 C. acetate with N-bromosuccinimide to form the corre- A mixture of 25 ml. of xylene and 3 m1. of 2,4,6-colspending 7-bromo derivative, and reacting this derivalidine was heated to boiling, and tothe hot solution was tive with collidine) in 125 ml. of purified dioxane was added, in small portions, two grams of 7-bromo-diosgenshaken under 3 atmospheres of hydrogen in the presence in-B-a-cetate. The resulting mixture was heated under of Raney nickel catalyst. reflux for an additional 15 minute period. The reaction One mol of hydrogen was absorbed in 40 minutes, and mixture was then cooled, washed successively with water, 7 crystalline material started to separate from the soluwith cold 1 N aqueous hydrochloric acid, and with 5% tion. The 7-dehydrotigogenin acetate was redissolved aqueous sodium bicarbonate solution' The organic layer by Warming slightly, and the catalyst was removed by was then dried .over anhydrous sodium sulfate, and the filtration. xylene was evaporated therefrom in vacuo to give a crys- The filtrate was concentrated to dryness, and the crystalline residue. The residual material was recrystallized talline residue was digested with 15 ml. of methanol.

The product was collected on a filter and was washed with methanol. Yield, 2.78 g.; M; P. 234-237 C.

Reerystallized from methanol, the product separated mo --CHl v v i 0 i no l EXAMPLE 7 Preparation of A -3-acet0xypregnadienone 20 CH: OH:

\ Thirty grams of A -3-hydroxy-20-keto 'pregnene was dissolved. in 100 cc.. of acetic anhydride, and the resulting solution was heated under reflux for a period of approximately three and one-half hours. The reaction was cooled, and'the crystalline material which separated was recovered by filtratiomand washed free of acetic anhydride with methanol to give substantially pure A-3-acetoxy-20-keto-pregnene; P. 147 148 0; [a];,=8' (C.=l.0l in chloroform). 1 H Three and six-tenths grams of A -3-acetoxy-20-ketopregnene was dissolved in 60 ccof carbon tetrachloride, 1.87 g." of N-bromosuccinimide was added, and the resulting mixture was heated under reflux for a period of approximately 20 minutes while illuminating the mixture with a photoflood light. At the end of this period, the photochemical reaction was interrupted, the reaction solution was cooled, and the cold solution was filtered to remove insoluble ,succinimide. The filtered solution was then evaporated in vacuo, and methanol was added to the residual material whereupon the latter crystallized and was purified by recrystallization from methanol to give substantially pure A' -3-acetoxy-7-bromo-20-keto-preg nene; M. P. 121 -12250.

One and sevenrtenths grams of A -3-acetoxy-7-bromo- ZO-keto-pregnene was mixed with 10 g. of dimethylaniline, and the mixture was heated on the steam bath for a period of approximately two hours. The reaction mixture was diluted with 100 cc. benzin and 50 cc. of benzene; and theresulting solution was washed successively with one 100 cc; portion of l N sulfuric acid, two 75 cc. portions of water, one 75 cc. portion of saturated, aqueous sodium bicarbonate solution, and finally with one 75 cc. portion of water. The washed organic layer was then driedover anhydrous sodium sulfate, and the dried solution was evaporated in vacuo to give crude A 3-acetoxy-pregnadienone-ZQ, which was obtained in'the form of an oil.

' EXAMPLE 8 Preparation of 3-acetory-A' -allqpregnenone-ZO on. on,

7.8 grams of A-"-3-acetoxypregnadienone-20 (prepared as described in Example 7 by reacting A -3-acetoxypregnenolone-20 with N-bromosuccinirnide to form the corresponding 7-bromo derivative, and reactingthis derivative with dimethylaniline) in 200 ml. benzene was hydrogenated in the presence of Raney nickel catalyst. After working up the product in the usual way, it was recrystallized from methanol to give 6.61 g. (87%) of leaflets, M. P. 170-175 C.

Analysis.-Calcd. for C I-1 0 C, 77.05; H, 9.56. Foundz C, 77.15; H, 9.30. j

Recrystallization from methanol raised the melting point to 172175.5 0., [111 The 3-acetoxy-A' -allopregnenone-20was subjected to alkaline hydrolysis to produce the corresponding 3-hydroxy compound having a melting point of 211-215 C.

Various changes and modifications may be made in carrying out the present invention without departing from the spirit and scope thereof. Insofar as these changes and modifications are within the purview of the annexed claims, they are to be considered as part of our invention. We claim:

1. A process of producing a A' -3 hydroxy steroid which comprises selectively reducing a A -3 hydroxy steroid with a Raney nickel catalyst and hydrogen in a neutral solvent to obtain a A -3 hydroxy steroid.

2. A process of producing a A' -3-acyloxy steroid which comprises selectively reducing a A -3-acyloxy steroid with a Raney nickel catalyst and hydrogen in a neutral solution to obtain the corresponding A' -3-acyloxy steroid, said acyl group being a lower fatty acid radical.

3. The process for preparing a A -3-acyloxyergostadiene which comprises reacting the corresponding acyl derivative of ergosterol with hydrogen in the presence of Raney nickel, said acyl group being a lower fatty acid radical. 1

4. The process for preparing A' S-acetoxy-ergOstadiene which comprises reacting ergosteryl acetate in an inert solvent medium with hydrogen in the presence of Raney nickel. i

No references cited. 

1. A PROCESS OF PRODUCING A$7-3 HYDROXY STEROID WHICH COMPRISES SELECTIVELY REDUCING A $5,7-3 HYDROXY STEROID WITH A RANEY NIKEL CATALYST AND HYDRGEN IN A NUETRAL SOLVENT TO OBTAIN A $7-3 HYDROXY STERIOD. 